Severe obesity causes substantially increased risk for morbidity and mortality. Bariatric surgery, in particular gastric bypass (GBP), is a useful treatment option for severe obesity because conventional weight-loss programs are usually unsuccessful for these patients. Nevertheless, wide variations occur in weight loss. Furthermore, GBP may not alter eating disturbances such as binge eating, and the initial improvement in psycosocial functioning after GBP may not be sustained. This study will examine these issues in morbidly obese subjects requiring GBP surgery.